It's used only as a dev dependency in 6 crates.

Depender (with downloads and own rev deps) bs64 version
140 1 mars-program dev ^0.1.2
3 ore-program dev ^0.1.2
marsh-program dev ^0.1.2
1 spam-program dev ^0.1.2
orz-program dev ^0.1.2
1 powx-program dev ^0.1.2